1. Field of the Invention
The present invention relates to the field of perforating guns used in a down hole oil well environment and in particular to a method and apparatus for using flourescent dyes to determine whether or not a tubing conveyed perforating (TCP) gun charge has fired.
2. Background of the Related Art
During the completion phase of an oil well, perforating guns containing explosive charges are lowered into the wellbore below the casing. Upon detonation the charges blast a hole in the casing, cement and reservoir rock, thereby enabling hydrocarbons in an adjacent hydrocarbon formation to flow into the wellbore for recovery. The conventional method for determining whether the perforating guns have successfully fired is to monitor changes in well bore pressure. Unfortunately, pressure monitoring can only indicate that one or more of the guns have fired (and not always reliably), but cannot determine or whether or not all of the guns have fired successfully. At present there is no known technology available for verifying whether each of the individual perforating guns have fired and hence, there is a lack of reliable quantitative downhole data in this regard. Without useful and reliable data, the decision making process is impaired, with attendant detrimental operational and economic effects. It is imperative that all downhole tubing conveyed perforating guns fire and penetrate the casing to optimize hydrocarbon flow and recovery from the adjacent formation. Thus, there is a need to reliably determine whether each of the perforating guns have successfully fired.
The present invention provides a method and apparatus for determining whether a tubing conveyed perforating (TCP) gun has fired by detecting a change in characteristics of the flow of an oil well. In one embodiment the present invention detects the presence of fluorescent tracer dye to determine whether or not a TCP gun has fired. In another embodiment the present invention detects a change is capacitance, or fiber optic electrical properties to determine whether or not a TCP gun has fired. In another embodiment of the present invention a method and apparatus is provided that detects the number of charges fired to determine whether or not all TCP guns have fired. The present invention also provides a method and apparatus for determining the contributions of injection wells to producing wells by introducing fluorescent tracers into injection wells and detecting the presence of the fluorescent tracers at production wells. In another embodiment of the present invention, a method and apparatus is provided for placing fluorescent dye particles in a gravel pack to sense when a gravel pack is deteriorating by detecting the tracer dye particles in the well flow.